1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to transmitting and receiving data, and, more particularly, to transmitting and receiving data, in which beam forming is performed in consideration of the communication capabilities of antennas of stations that perform directional communication in a high-frequency band.
2. Description of the Related Art
As networks become wireless and the demand for large multimedia data transmission increases, there is a need for studies on an effective transmission method in a wireless network environment. In particular, the demand for various home devices that wirelessly transmit high-quality video, such as digital video disk (DVD) images or high definition television (HDTV) images, is growing.
The IEEE 802.15.3c task group is developing a technological standard for transmitting large-volume data over a wireless home network. The technological standard, which is called “millimeter wave” (mmWave), uses an electromagnetic wave having a physical wavelength of a millimeter (i.e., an electromagnetic wave having a frequency band of 30-300 GHz) to transmit large-volume data. This frequency band, which is an unlicensed band, has conventionally been used by communication service providers or used for limited purposes, such as observing electromagnetic waves or preventing vehicle collision.
FIG. 1 illustrates a diagram for comparing the frequency bands of the IEEE 802.11 series of standards and mmWave. Referring to FIG. 1, the IEEE 802.11b or IEEE 802.11g standard uses a carrier frequency of 2.4 GHz and has a channel bandwidth of approximately 20 MHz. In addition, the IEEE 802.11a or IEEE 802.11n standard uses a carrier frequency of 5 GHz and has a channel bandwidth of approximately 20 MHz. In contrast, mmWave uses a carrier frequency of 60 GHz and has a channel bandwidth of approximately 0.5-2.5 GHz. Therefore, it can be understood that mmWave has a far greater carrier frequency and channel bandwidth than the related art IEEE 802.11 series of standards. When a high-frequency signal (mmWave) having a millimeter wavelength is used, a very high transmission rate of several Gbps can be achieved. Since the size of an antenna can also be reduced to less than 1.5 mm, a single chip which includes the antenna can be implemented. Furthermore, interference between devices can be reduced due to a very high attenuation ratio of the high-frequency signal in air.
A method of transmitting uncompressed audio or video data (hereinafter, referred to as uncompressed audio/video (AV) data) between wireless devices using a high bandwidth of a millimeter wave has recently been studied. Compressed AV data is generated after lossy compression processes such as motion compensation, discrete cosine transform (DCT), quantization, and variable length coding (VLC) processes. In so doing, components of compressed AV data that human visual and auditory senses are less sensitive to are removed. In contrast, uncompressed AV data includes digital values indicating pixel components (for example, red (R), green (G) and blue (B) components).
Stations that transmit/receive data in such a network environment are generally equipped with antennas. A transmitting station may have a different antenna from that of a receiving station. For example, a transmitting station may be equipped with a phased-array antenna, and a receiving station may be equipped with a single antenna. In this case, even if the transmitting station attempts to perform beam forming through the exchange of an antenna weight vector (AWV), the receiving station may not be able to respond to the transmitting station, and, thus, the beam-forming operation may not be properly performed.
Therefore, it is necessary to develop a technique of effectively performing beam forming even when a transmitting station and a receiving station have different types of antennas.